The presence of dissolved gases, including hydrogen, oxygen and nitrogen, in metals, for example, steels can cause several undesirable effects, such as, internal ruptures or flaking, embrittlement, void formation and inclusions. It is desirable, therefore, to remove the dissolved gases prior to solidification of the metal and vacuum often is employed for such purpose. The molten metal is housed in a large chamber and is agitated to facilitate removal of the gases by vacuum applied to the chamber. This prior art operation, however, is somewhat unsatisfactory, in that a molten metal to be treated must be tapped from a furnace with sufficient temperature to withstand heat losses during treatment, and efficient removal of the gas is not achieved.